This invention relates to flexible polyurethane foam and methods for its preparation.
Polyurethane foams are widely used in many packing, cushioning and other applications. These foams are usually prepared by reacting a polyisocyanate with a relatively high equivalent weight active hydrogen-containing composition in the presence of a blowing agent. In most commercial foam formulations, water is used as a primary blowing agent, and low boiling halocarbons are used as "auxiliary" blowing agents. These auxiliary blowing agents contribute gases which cause the polymer to expand into a cellular structure. In addition, they soften the foam and during processing act as a heat sink, thereby preventing the exotherm from the polymerization reaction from degrading the polymer.
The most common auxiliary blowing agents are low boiling hard chlorofluorocarbons (CFCs) such as CFC-11 and CFC-12, which in recent years have been attacked as contributing to the destruction of the ozone layer of the atmosphere. Accordingly, the continued use of these hard CFCs is being increasingly restricted. For this reason, it is desirable to provide alternatives to these hard CFC blowing agents.
However, because of the several roles the auxiliary blowing agents play in the preparation of polyurethane foam, it has been difficult to find acceptable substitutes. Many potential substitutes are prohibitively expensive. Others present unacceptable fire or toxicological risks. Many other potential substitutes provide blowing, but fail to adequately soften the foam or absorb enough of the reaction exotherm.
Thus, it is desired to provide a blowing agent for flexible polyurethane foam which performs the functions of conventional auxiliary blowing agents, yet is safe and affordable.